Looking Up: Locate Neptune with binoculars

Friday

Sep 22, 2017 at 1:23 PMSep 22, 2017 at 1:23 PM

By Peter Becker More Content Now

If you have a pair of 7x 35 binoculars (or larger), try and spot the planet Neptune the next clear night. I suspect that not many on the block can say they have seen Neptune. The eighth planet from the Sun isn’t too hard to find this season, being situated very close to a star visible to the unaided eyes, in the evening sky.

Uranus and Neptune are both giant planets, with fascinating stories all their own. They are so distant, however, they never appear like a bright star in Earthen skies. Unlike any of the other planetary neighbors, from Mercury to Saturn, they usually escape public attention.

Uranus can be faintly visible to unaided eyes if you have excellent, moonless skies, and know just where you are looking. Neptune requires a pair of binoculars. Both will require a chart showing their slow path in front of the background stars. They appear like another dim star even with binoculars, but the thrill is knowing that these are distant planets all their own.

They are so far, a small telescope will show only a little more, revealing they are more than a star-like “pin point” but show a tiny disc under enough magnification and with good sky conditions.

In late September, if you go out around 9 - 10 p.m., to locate Neptune you will need to face south-southeast and trace the constellation Aquarius the Water Bearer. First look for the huge square of stars rising in the southeast- the “Great Square of Pegasus.” To the right of the square, look for a squat parallelogram of stars, with a star within this shape. This is part of Aquarius and is often pictured as the Water Bearer’s head. Look down (south) from this group of stars to find the first fairly conspicuous star (magnitude +3.7). This is the star Lambda Aquarii. Using binoculars, Neptune will be visible as a dim star (magnitude +7.8) less than one degree below (south-southeast) Lambda. (One half degree is about the apparent width of the Moon.)

The planet is moving very slowly in its apparent path, and will stays in this same general area through next February.

With a small telescope at low power (about 30x- 40x), Lambda and Neptune will appear in the same field of view, or close to it. The planet will appear as a pale blue star. With magnification of 150x to 200x, Neptune will appear as a very slight, bluish disc.

Neptune takes 165 years to go once around the Sun. About four times as big as Earth, the planet is 30,598 miles wide. It is a very windy planet, with wind measured at 1,500 m.p.h., more than on any other planet. It’s very cold there; the average temperature is -353 degrees Fahrenheit. There are 14 known satellites; its largest, Triton, is a rebel for sure: it orbits Neptune backwards.

Just imagine all this as you stare at this dim blue speck!

It’s best to look before the Moon is close to full. First quarter Moon is on September 27.

See www.skyandtelescope.com for more information and more detailed star charts to find Neptune as well as Uranus.

Keep looking up!

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Peter Becker is Managing Editor at The News Eagle in Hawley, PA. Notes are welcome at news@neagle.com. Please mention in what newspaper or web site you read this column.

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